1. Field of the Invention
The present invention relates to electrostatographic copiers and or copier/printers and more particularly, to methods and apparatus for providing improved density consistency and uniformity in such copiers or copier/printers.
2. Description Relative to the Prior Art
In the prior art as presented by U.S. Pat. No. 4,710,785, it is known to provide an electrostatographic copier machine with adjustable process control parameters wherein image contrast, density and color balance can be adjusted. The process control parameters considered adjustable are initial charge V.sub.o, exposure E.sub.o and developer bias.
In order to control the quality of the apparatus, the referenced patent discloses the production of a test print and the scanning of the test print by the copier scanner. The scanned data of the test print is compared to a signal stored in memory regarding generation of the original. As a result of the comparison, an error signal is generated and adjustments made accordingly.
A problem associated with the above is that nonuniformities in a direction that is cross-track to the process direction cannot be well accommodated by making overall process changes. It is to this problem that the instant invention is addressed.
The invention is further directed to the problem of overcoming drift in an electrostatographic process wherein over time recalibration is required.